Height-adjustable chairs and table pedestals are known of the general type having a lifting means consisting of a hydraulic lifting cylinder and a piston rod telescopically extendable therefrom, said lifting means being connected axially at one end with a height-adjustable plate and at the other end with a base, and with a pump assembly driven by an energy source, said pump assembly being connected with the lifting cylinder in the vicinity of its free end by a line for charging the lifting means with pressure-transmitting fluid.
Chair or table pedestals of this type are used for dentists' chairs and operating tables. In these, an electric motor-pump assembly is mounted on the base, and is used to charge the hydraulic lifting means with pressure-transmitting fluid. The electric motor is normally supplied with electricity from a wall socket. Furthermore, since such operating tables or dentists chairs are very bulky, and especially because they often have shrouds around their lower parts, esthetic problems are of no concern.
Moreover, tables with multiple pedestals are known, which are height-adjustable by means of spindle-and-nut drives powered by electric motors. Such height-adjustable tables pedestals are extremely complex from the structural standpoint. Also known are barbers' chairs which are often pumped by hand.